Manage signature help sessions

Hi all,

I would like to manage the signature helps of my methods.

Currently I created an mef project, that use CreateSignatureHelpSession from ISignatureHelpBroker to create signature sessions.

when I recognize an open parenthesis , I create the session and start it, when I recognize an close parenthesis, I dismiss the session. 

I would like to back to older sessions , if there is a method inside another method.

for example:

min(1,max(

will display the signature help of the max method

and after close the parenthesis , I will display the signature help of the older one- the min method.

How should I support it?

I didn't find any explanation or example.

Thanks.